Similarly, the ACT's hospital system have the lowest proportion of specialist services with no gap, at just 78.5 per cent, compared with most other states at about 85 per cent.

Yet despite having the highest rates of private health insurance coverage in the country, many Canberrans are using the public hospital system without claiming against their hospital cover.

While Medicare covers 75 per cent of scheduled, or standard, fee for hospital services, while private health insurance usually covers the remaining 25 per cent, but cover can vary greatly.

But specialists like surgeons and anaesthetists can charge much more than the Medicare Schedule fee, and only most insurers will only cover some specialists' full fees under prearranged 'access cover' with those doctors.

Healthcare Consumers Association of the ACT executive director Darlene Cox said the problem was that consumers were being caught in a "hotly contested" national fight over cost-shifting between states, the Commonwealth and public and private health systems.

As a result, she said, patients were getting conflicting advice from their health insurers and staff in the public hospital system.

"The private health insurers are discouraging their members from using it (in a public hospital), because the government's already paying, and then you have public hospitals encouraging them to use it, often saying that 'this is an opportunity to help your local hospital'," she said.

But, Ms Cox said that irrespective of the funding dispute, the higher gap charges in the ACT were a symptom of the market - partly due to being in a "regional area" with fewer specialists, and a "lack of transparency" around specialists fees.

The "gap", or out-of-pocket payment, is the difference between what Medicare and private health insurance cover, and the actual fees hospital specialists charge, that a private patient pays.

As a result, despite the ACT having the highest rate of PHI coverage - at 57.7 per cent for hospital cover and 68.3 per cent for general treatment cover - just 10.3 per cent of public hospital patients actually used private cover in 2014-15 - ACT Health did not provide data for 2015-16.

That report estimated the practice was growing at about 10 per cent a year between 2008-09 and 2014-15 and Private Healthcare Australia, which represents insurers, have urged the federal government to address the issue, which it estimates amounts to $1 billion a year in 'cost-shifting'.

It is understood the federal government is still considering the options private health insurance reform after a review of the system started in 2015-16.

A spokeswoman for ACT Health said low use of private health insurance did place "additional pressure" on the public health system, as does growing demand; but it could also be a "reflection of the trust the community has in the (public) care they receive".

She said the private sector also played ":an important role in the delivery of quality health care in our city" and private health insurance reforms rested with the Commonwealth government.